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Abstract

The tunneling of surface plasmon-polaritons (SPPs) across an interruption in the metallic film supporting them is numerically investigated in details. Both non-symmetrical and symmetrical geometries are considered. A very high tunneling efficiency is calculated for the long-range surface plasmon in the symmetrical geometry, with an amplitude transmission as high as 80% over a 5 μm gap for a 40 nm thick gold film illuminated at λ=785nm. The transmission is somewhat lower in the non-symmetrical geometry. The coupling between the different SPP modes (radiative and non-radiative) in that geometry is also investigated in detail. This coupling depends periodically upon the length of the gap. Overall, the results indicate that SPPs are not very sensitive to technological imperfections and can survive large waveguide interruptions.

Figures (10)

Fig. 1. Sketch of a metallic waveguide with thickness t and an interruption d. Two SPP modes can propagate in that system. (a) Excitation with an air mode and (b) with a substrate mode. For clarity, modes reflected backwards at the interfaces are not shown.

Fig. 2. Amplitude of magnetic field when an air SPP mode is propagating on a t=50 nm thick gold film with a d=700 nm interruption, see Fig. 1(a). The movie shows the field distribution for interruptions between d=50 nm and d=4.7 μm. [Media 1]

Fig. 4. Relative average amplitude of the field transmitted through the gap measured (a) 5 nm above and (b) 5 nm below the metallic film, as a function of the interruption length d in the film. The air mode is used for excitation, see Fig. 1(a).

Fig. 5. Relative average amplitude of the field transmitted through the gap measured 5 nm below the metallic film, as a function of the interruption length d in the film. Two different substrates are considered, with respective index n=1.47 and n=1.8.

Fig. 6. Relative average amplitude of the field transmitted through the gap measured (a) 5 nm above and (b) 5 nm below the metallic film, as a function of the interruption length d in the film. The glass mode is used for excitation, see Fig. 1(b).

Fig. 7. Symmetrical geometry where a metallic waveguide with thickness t and an interruption d is embedded in two similar dielectrics. Two SPP modes can propagate in that system: (a) long-range mode and (b) short-range mode. The amplitude of the magnetic field is sketched and any reflected mode is omitted for clarity.

Fig. 8. Amplitude of magnetic field when a LR SPP mode is propagating on a t=40 nm thick gold film with a d=700 nm interruption, see Fig. 7(a). The movie shows the field distribution for interruptions between d=50 nm and d=4.7 μm.

Fig. 9. Amplitude of the magnetic field 5 nm above the t=40 nm thick metallic film (see the dashed lines in Fig. 7) for long-range (LR) and short-range (SR) excitations. The film has a d=700 nm long interruption.

Fig. 10. Relative average amplitude of the field transmitted through the gap measured 5 nm above the metallic film, as a function of the interruption length d in the film. Both excitations with LR and SR modes are investigated.